1. Field of Invention
The present invention relates to insulating blocks for lining furnace walls and apparatus for mounting such insulating blocks.
2. Description of Prior Art
It has been known to use refractory bricks or structure to line furnaces, as exemplified in U.S. Pat. Nos. 741,629; 1,701,480; 1,813,790; 2,368,265; 3,302,356; 3,362,689 and 3,630,503.
Ceramic fibers or blankets made from refractory fibrous materials such as chromia-alumina-silica, alumina-silica compositions and zirconia compositions have become desirable as furnace insulation because of their ability to withstand high temperatures. In the past, efforts have been made to attach the fiber or blanket material to the furnace wall using stainless steel attachment structure, but this attachment structure has often been unable to withstand the high temperatures present at the insulation surface and melted or otherwise failed. Further, the ceramic fibers tended to vitrify and shrink during long exposure to high temperatures.
Also, other prior art efforts, such as in U.S. Pat. Nos. 2,341,777; 3,147,832; 3,523,395; 3,687,093; 3,738,217; 3,742,670 and 3,771,467, were made to impale or spear the ceramic blanket on a pin or stud mounted with the furnace wall, with a washer mounted at the end of the stud to hold the blanket in place. However, the blanket tended to sag and tear away from the furnace wall with this structure. Also, the studs served as conduits for heat through the blanket to the furnace wall.
Other similar apparatus, such as in U.S. Pat. No. 3,832,815 were in the form of modules formed from blankets or strips of ceramic fiber material. However, the strips of ceramic material were punctured or pierced by connecting pins when mounted in modules, and the fiber blankets would thus tend to fall away from the pin in the area of the holes where the blankets were pierced by the pin.
Other panels, such as in U.S. Pat. No. 3,605,370 used ceramic wool blankets mounted over refractory blocks, held in place with the blocks by alloy rods in folds of the blankets in spaces between adjacent blocks. With this construction, the blankets were laid flat over the blocks and susceptible to shrinkage. Further, a direct path to the support wires was present between adjacent folds of the blanket for passage of heat and corrosive elements of the furnace atmosphere to the support wires.